Studies on fluid balance of the calf. 1

The isotope dilution technique was applied to clinically intact calves to measure total body fluid volumes by means of tritium water and blood plasma volumes by means of 125I-human serum albumin. The principle of double marking was applied for parallel recording of both the volumes in a single blood plasma sample. Intravenous injection of tritium water was followed by almost exponential decline in blood activity concentrations. Most of the tritium water was distributed all over the organism after 60 minutes. Intravenous administration of 125I human serum albumin caused massive dislocation of the radioindicator from the vasal space. This tracer, consequently, was found to be only of limited importance for blood plasma volume measurements. Follow-up tests were continued up to 14 days from injection of tritium water and revealed for clinically intact calves a half-life of 5.7 days for body fluid as well as body fluid discharge proportions of 56 per cent through urine, 38 per cent through respiration and skin, and 6 per cent through feces. The body fluid metabolism of the calf was balanced by means of a mathematical model. Calculated results were compared with experimental findings. (author)